Is there any reason why my repository methods should not be static?

I have been working with an MVC app and creating Repositories that manipulate, validate, update, and read/write data. All of them are static. Here is an example:

public static int Create(user u)
{
      using(DataContext db = new DataContext())
      {
          //do the thing and submit changes...
      }

      //return the new user id
}

(Note: this is just a sample, I am not looking for tips about creating users or returning user ids, etc.)

Then I can just call int id = RepoClassName.Create(userVariable);

Is there anything wrong with using static methods like this? I just don't see why I should need to instantiate an object to do this.